Diesel engines



Oct. 13, 1964 M. l. PETROFF 3,152,584

DIESELENGINES Filed March 4, 1965 INYENTOR. MICHAEL I. PETROFF United States Patent Office 3,152,584 Patented st. 13, 1954 3,152,584 DESEL ENGINES Michael I. Petrofi, 362A Lexington St, San Francisco, Calif. Filed Mar. 4, 1963, Ser. No. 262,740 3 Claims. (Cl. 123-439) This invention relates to improvements in diesel engines and more specifically to improvements therein whereby the efficiency of existing diesel engines may be increased.

It is a primary object of this invention to increase the efi'iciency of diesel engines by decreasing the time required to inject fuel into the cylinder without decreasing the amount of fuel injected on each cycle.

As an aid to the understanding of the present invention, the operation of a conventional four-cycle diesel engine to which the invention applies should be reviewed. On the intake stroke, air is drawn into the cylinder by the action of the piston traveling downwardly in the cylinder. The piston then moves upwardly in the cylinder to compress the air therein, causing the temperature of the air to rise to a temperature higher than the ignition point of the fuel to be injected.

Fuel is then injected by a reciprocating fuel pump piston into the cylinder. Fuel injection normally begins near the end of the compression stroke and ends near the beginning of the power stroke. Ignition Will occur before the end of the compression stroke, and the energy of the igniting fuel will oppose further upward movement of the piston, with a consequent waste of power. The upward piston movement will continue, however, by virtue of the power delivered to the engine crankshaft by the other pistons of the engine.

After the piston has completed its compression stroke, it will now move downwardly under the impetus of the expanding ignited fuel to deliver power to the crankshaft. Upon completion of the power stroke the piston will again move upwardly to exhaust the cylinder of gases, to complete the four cycles of the engine.

Timing of the fuel injection is conventionally accomplished by means of a camshaft geared to the crankshaft. A cam lobe on the camshaft engages a cam follower to force the fuel pump piston in a direction to inject the fuel in the fuel pump into the main cylinder. In order for the fuel pump piston to inject all of the fuel necessary for the power stroke, it must move through a stroke determined by the height of the cam lobe. However, as I have realized, the height of the cam lobe also dictates the time duration of the stroke of the fuel pump piston. That is, the angle of slope of the cam rise must be sufficiently small so that the fuel pump actuator can easily follow the cam lobe. If the slope of the conventionally shaped cam lobes were increased in order to shorten the length of time of the fuel pump operator stroke, the rise would become too abrupt, causing failure of the fuel pump actuator cam follower and consequently the engine. Thus, in order to obtain the desired length of stroke of the fuel pump piston, the conventional diesel engines utilize cam operators having a relatively high cam lobe resulting in a relatively long duration of fuel pump operation. As merely one example, in the automotive type six-cylinder diesel engines produced by the Hercules Motors Corporation, Canton, Ohio, fuel injection starts while the main piston is traveling on its compression stroke approximately 18 before top center (referring to rotation of the cranks on the crankshaft), and ignition begins approximately l0 before top center. Injection continues until approximately 14 past top center.

As mentioned above, all ignition of fuel before the compression stroke ends, i.e., when the piston is at top center, is wasted since it acts to oppose the completion of the compression stroke. In order to reduce this wasted power, I propose to delay the injection of fuel into the cylinder until the compression stroke is more nearly complete. Then less power will be Wasted and more power will be available to the power stroke. This delay, however, cannot be accomplished merely by adjusting the position of the cam lobe on the camshaft to begin fuel pump operation later in the engine cycle, since this would delay the full injection of the fuel into the piston until too late in the power stroke, which would create an inetficiency well overcoming the saving in power produced by the initial delay in injection.

What I propose to do is to delay the fuel injection by shortening the total time of fuel injection, so as to start the injection of the fuel as near the end of the compression stroke as possible without delaying the end of the injection beyond an inefficient point.

The shortened period of fuel injection cannot be accomplished, however, by merely decreasing the angular width of the cam lobe, since if this is attempted the angle of cam lobe slope becomes so steep that the cam lobe follower on the fuel pump operator cannot follow the lobe. On the other hand, the angular width of the cam lobe cannot be decreased while maintaining the same angle of slope, because then the height of the cam lobe would be lessened, in turn reducing the length of stroke of the fuel pump piston. This stroke, however, must remain the .same in order to get the proper amount of fuel injected into the cylinder.

In order to accomplish the object of my invention, 1 propose to decrease the time duration of the fuel pump stroke while maintaining the same length stroke by reduicng the length and height of the cam lobe and by providing means between the cam lobe and the fuel pump piston actuator to multiply the movement produced by the cam lobe by an amount equal to the reciprocal of the amount of height reduction of the cam lobe.

In the drawings, forming a part of this application, and in which like parts are designated by like reference numerals throughout the same,

FIG. 1 is a fragmentary vertical section through a typical diesel engine to which my invention has application.

FIG. 2 is a view similar to that of FIG. 1 illustrating the manner in which the engine of FIG. 1 has been modified in accordance with my invention.

FIG. 3 is an enlarged view of a portion of FIG. 2 illustrating the details of my improvement.

FIG. 4 is a view of the connecton between the fuel pump piston actuator and the cam-movement multiplying device of FIG. 3.

FIG. 5 is a view of the cam of FIG. 2 showing the manner in which it is modified from that used in the engine depicted in FIG. 1 to accomplish the objects of the invention.

Referring now to the drawings, FIG. 1 represents a typical diesel engine and shows a crankshaft 10 which is driven by a plurality of connecting rods 11 attached to cranks 12 on the crankshaft. Each connecting rod 11 is attached to a piston 13 disposed for reciprocation within a cylinder 14. At one side of and parallel to cranskshaft 1t) is camshaft 15, which is driven from the crankshaft by the usual gear train, not shown but indicated by the dotted line 16. In a four-cycle engine the camshaft 15 rotates at half the speed of the crankshaft. Camshaft 15 has a plurality of cams 17 thereon, there being one cam 17 for each cylinder 14. As camshaft 15 rotates, the cam lobe 18 on cam 17 engages the cam follower end 19 of fuel pump piston actuator 29 to push the actuator upwardly. This motion is transmitted through rocker lever 21 to force the fuel pump piston 22 downwardly. As a result, fuel introduced into the fuel pump 23 through conduit 24 is injected through orifice 26 into the cylinder 14. The

fuel pump piston actuator 19 reciprocates in bearings 27 which are fixed to the engine frame.

Cam lobe 18, as seen in FIG. 5, has a total angular width indicated by arrow 18a, which is the total of the angular widths 18b and 13c of the rising face 18d and falling face 13a of the lobe, and the height of the lobe at its maximum point 18; is indicated by the arrow 18g.

The engine illustrated in FIG. 1 operates in a manner as previously described, with the fuel injection stroke beginning when the cam follower end 19 of rod 2Q engages the beginning of cam lobe face 18d at a time before the crank 12 reaches top center. Fuel injection will be complete when the maximum point of rise 13 of cam lobe 18 engages the cam follower end 19 of rod 24), which will occur after the crank 12 has passed top center. As the cam follower end of rod 29 rides down cam face 18c the fuel pump piston 22 will retract upwardly to complete the fuel injection cycle.

In order to accomplish the objects of my invention, the camshaft 15 is moved from the position shown in FIG. 1 to the position 115 shown in FIG. 2, and the earns 17 thereon are replaced by earns 117 which have the same radius as cams 1'7 but which have modified cam lobes 113. The ratio of the gear connection between camshaft 115 and crankshaft 10 represented by dotted line 116 is main tained the same as before. As best seen in FIG. 5, the cam lobes 118 are modified from lobes 13 by reducing the angular width 118a thereof to half the former width 18a, and by reducing the maximum height 118g to half the former height 18g. The rising and falling faces 113:! and 118@ each have an angular width 1181; and 1180 that is half the former angles 18b and 18c so that the angle of slope of the faces 118d and 118@ is the same as the cam lobe 18.

A lever arm 131 is journaled at one end for oscillatory movement on shaft 132, fixed to the engine block, and carries cam follower roller 133 at its midpoint. The other end of arm 131 is bifurcated at 134 to receive link 135 which is journaled on pin 136 carried by the lever arm. Formed on the upper end of link 135 is the lower half 136 of a slide block connection 137. The upper half 138 of slide block connection 137 is secured to the lower end of the fuel pump piston actuator rod 21 The four-cycle operation of the engine of FIG. 2 is identical to that previously described, the only difference being the relationship of the fuel pump operation to the reciprocation of the piston 13. In FIG. 2 the beginning of the feeding stroke of the fuel pump piston 22 is delayed until the cam follower 133 engages the beginning of the rising face 113d of cam lobe 118, which, as is apparent from FIG. 5, will be later in the compression stroke of piston 13. The fuel pump piston will complete its feeding stroke when the cam follower roller 133 reaches the maximum point of rise 118 of lobe 118, at the same point of time as in the operation of the engine illustrated in FIG. 1. Since the slope of cam faces 118d and 113a is the same as before, the cam follower 133 can follow cam lobe 118 as easily as the cam follower end 19 of rod can follow cam lobe 18.

It will be noted, of course, that with cam lobe 1118 reduced in height by half, the movement of cam follower 133 will be reduced in half as compared to the movement produced by cam lobe 18. However, since the cam follower 133 is at the mid-point of lever arm 131, the end 134 thereof will move through twice the distance produced by cam lobe 118. Thus, even though the movement of cam follower 133 is reduced, this movement is multipled by the cam lever arm 131 so that the movement of rod 20 is the same as before, so that the length of the stroke of the fuel pump piston is unchanged.

As is thus apparent, I have been able to reduce the time of fuel injection without decreasing the amount of fuel injected thus enabling fuel injection to be accomplished during less of the compression stroke of piston 13 with an attendant saving in power and efiiciency.

In the engine illustrated in FIG. 1, the start of fuel injection will begin when the piston is traveling upwardly in its compression stroke at approximately 13 before top center so that injection will occur during approximately 18 of rotation of the crank 12 to its top center position. During this time, ignition of the injected fuel will oppose the completion of the compression stroke, requiring power to be taken from the other cylinders to finish the compression stroke. On the other hand, with the use of my invention, the start of fuel injection is delayed until later in the compression stroke, when the crank 12 and piston 13 are closer to their top center position. The injected fuel that is then ignited opposes much less of the compression stroke, enabling more power from the other cylinders to be utilized for useful work rather than being utilized to force the piston upwardly against the force of the igniting fuel in the cylinder. For example, if the fuel injection time during the compression stroke is decreased by one half, then at least one half of the otherwise wasted power delivered by the other pistons will be available at the crankshaft for useful work.

I have found that the maximum efficiency of conventional diesel engines can be obtained by halving the time of fuel injection. Efliciency can be increased, although not as much, by smaller reductions in time, i.e,, where the angular width 118a of lobe 118 is more than half of that of lobe 18. Theoretically, the efliciency would increase if the angular width 118a of lobe 113 where less than half of lobe 18 up to a point when no fuel is injected into the cylinder during the compression stroke of piston 13. However, if the time of injection is made too short, then the fuel will no vaporize sufficiently at its passes through nozzle 26 and it will not ignite properly in the cylinder.

If the angular width of cam lobe 118 is decreased in half, as above, then the maximum height 118g of the lobe should also be decreased by half so as to maintain the same slope of the cam faces. However, the maximum height 118g could be somewhat more or less than half the former height and still give the same results. Naturally, if the reduction of height is some other proportion than half the former height, then the cam follower 133 should be located on lever arm 131 at such a point that the multiplication of movement is the reciprocal of the proportion of height reduction so that the stroke of rod 20 remains the same. Thus, if the height of the cam lobe is reduced to 60%, then the multiplication factor of lever arm 131 should be 1.667.

Although the above description has concerned itself with four-cycle diesel engines, it is apparent that the same advantages can be obtained in two-cycle diesel engines by decreasing the time heretofore required for fuel injection.

It is to be realized that the form of the invention illustrated and described herein is to be taken as a preferred embodiment of the same, and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit of my invention or the scope of the attached claims.

Having described my invention, I claim:

1. The method of improving performance of a diesel engine having a piston operating on a crankshaft to reciprocate in a cylinder, a fuel pump connected to deliver fuel to said cylinder, a camshaft, a cam fixed on said camshaft for rotation therewith and having a cam lobe thereon, said cam lobe having a beginning of rise, a maximum point of rise and an end of rise, a cam follower in engagement with said cam, and a fuel pump operator actuated by movement of said cam follower, said camshaft being geared to said crankshaft and said cam being fixed to said camshaft such that said cam roller engages the beginning of rise of said cam prior to the completion of the compression stroke of said piston, the method comprising:

decreasing the angular width of said cam lobe between the beginning of rise of said cam lobe and the point of maximum rise thereof While retaining the same angular position of the point of maximum rise of said cam lobe by a given ratio;

decreasing the radial angle of said cam lobe between the point of maximum rise of said lobe and the end of rise of said lobe by the same ratio;

decreasing the maximum height of said cam lobe by a given proportion; and

multiplying the movement of the fuel pump operator produced by the cam follower by the reciprocal of given proportion.

2. In a method as set forth in claim 1 wherein said ratio is one half.

3. In a method as set forth in claim 1 wherein said ratio and said proportion are both one half.

References Cited in the file of this patent FOREIGN PATENTS OTHER REFERENCES Cams, by Harold A. Rothbart, John Wiley and Sons, Inc., New York, 1956, call letter TJ206R6; pages 107, 

1. THE METHOD OF IMPROVING PERFORMANCE OF A DIESEL ENGINE HAVING A PISTON OPERATING ON A CRANKSHAFT TO RECIPROCATE IN A CYLINDER, A FUEL PUMP CONNECTED TO DELIVER FUEL TO SAID CYLINDER, A CAMSHAFT, A CAM FIXED ON SAID CAMSHAFT FOR ROTATION THEREWITH AND HAVING A CAM LOBE THEREON, SAID CAM LOBE HAVING A BEGINNING OF RISE, A MAXIMUM POINT OF RISE AND AN END OF RISE, A CAM FOLLOWER IN ENGAGEMENT WITH SAID CAM, AND A FUEL PUMP OPERATOR ACTUATED BY MOVEMENT OF SAID CAM FOLLOWER, SAID CAMSHAFT BEING GEARED TO SAID CRANKSHAFT AND SAID CAM BEING FIXED TO SAID CAMSHAFT SUCH THAT SAID CAM ROLLER ENGAGES THE BEGINNING OF RISE OF SAID CAM PRIOR TO THE COMPLETION OF THE COMPRESSION STROKE OF SAID PISTON, THE METHOD COMPRISING: DECREASING THE ANGULAR WIDTH OF SAID CAM LOBE BETWEEN THE BEGINNING OF RISE OF SAID CAM LOBE AND THE POINT OF MAXIMUM RISE THEREOF WHILE RETAINING THE SAME ANGULAR POSITION OF THE POINT OF MAXIMUM RISE OF SAID CAM LOBE BY A GIVEN RATIO; DECREASING THE RADIAL ANGLE OF SAID CAM LOBE BETWEEN THE POINT OF MAXIMUM RISE OF SAID LOBE AND THE END OF RISE OF SAID LOBE BY THE SAME RATIO; DECREASING THE MAXIMUM HEIGHT OF SAID CAM LOBE BY A GIVEN PROPORTION; AND MULTIPLYING THE MOVEMENT OF THE FUEL PUMP OPERATOR PRODUCED BY THE CAM FOLLOWER BY THE RECIPROCAL OF GIVEN PROPORTION. 